One-time use cameras are widely available that are sold preloaded with film and a battery or batteries for a flash unit included in the camera. Such cameras are typically made by first assembling a camera frame assembly including a frame, flash unit, battery, and front cover. The camera frame assembly is then tested for proper operation of the flash unit and the camera frame assembly is then moved to a darkroom for film loading. The term "camera frame assembly", as used herein, to refer to both a completed camera and incomplete assemblies, including a frame and one or more other parts, that will be assembled with more parts to form the completed camera. Where necessary to understanding, the state of completion of a camera frame assembly is indicated by context.
The film in these cameras is commonly prewound for winding back into the canister of a film cartridge during use. A variety of different procedures for prewinding the film are known. In some of these, such as procedures disclosed in U.S. Pat. No. 5,895,126, the film is prewound within one of the two film chambers of a camera frame assembly. (This film chamber is also referred to herein as the scrolling chamber.) The film winding is in the dark, with the back of the camera open. The back of the camera is then closed to render the camera light-tight, for example, by attaching a back cover.
The scrolling chamber is part of a plastic camera body member, such as a frame, that is included as part of a camera frame assembly. The support layer of the film is also plastic. The polymers used for the scrolling chamber and the film are dielectrics and are often subject to triboelectric charging when rubbed against each other. As a result, the scrolling chamber, the rest of the camera body member, and the camera frame assembly as a whole can be subject to static electrification, under some ambient conditions, depending upon the polymers used for the scrolling chamber and film, the humidity and other factors. The static charging is temporary and rapidly dissipates, under most conditions, into the surrounding environment.
U.S. Pat. No. 5,574,337 discloses flash devices having a self-oscillating charging circuit employing high feedback gain to maintain oscillations. Static electrification is particularly problematic for cameras having such self-oscillating flash charging circuits. The high feedback gain makes the flash circuit susceptible to electrostatic start up. Since the flash circuits include a flash ready light, electrostatic start up during or immediately after darkroom film winding is likely to result in the flash ready light turning on and the film being fogged.
U.S. Pat. No. 5,634,153 discloses flash devices having a self-oscillating charging circuit in which a resistor can bleed down small amounts of electrostatic charge caused by normal handling of the camera or other device. U.S. Pat. No. 5,761,451 discloses a one-time use camera having a self-oscillating charging circuit having a bleed down resistor, and indicates that during film loading, it is possible for an electrostatic charge to be generated that is too great for the bleed down resistor to bleed down quickly enough to prevent electrostatic starting and resultant darkroom film fogging. U.S. Pat. No. 5,761,451 discloses the use of a shorting wire, during darkroom film loading to short the flash charging circuit and thus prevent electrostatic starting. Holes are provided in a front cover of the camera body to provide access for the shorting wire. U.S. Pat. Re. 34,168 is similar. This approach effectively controls electrostatic starting, but requires careful positioning of a shorting wire or the like through access openings.
U.S. patent application Ser. No. 09/149,688, filed Sep. 8, 1998, discloses a camera flash charging apparatus for a one-time use camera that is subject to starting when a battery is connected to the circuit.
U.S. Pat. No. 5,337,099 discloses a one-time use camera in which an insulating tape is disposed between a battery terminal and battery contact. The tape protrudes through an opening in the camera body and is attached to a wrapper that encloses the camera. When the user tears off the wrapper, the tape pulls out.
It would thus be desirable to provide improved methods for loading a camera frame assembly in which unintended starting of flash charging can be prevented without shorting the flash circuit and despite the presence of a battery.